This invention relates to power transmissions and, more particularly, to power transmissions having three planetary gearsets and providing at least seven forward speed ratios.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost.
It is an object of the present invention to provide an improved low-content power transmission having at least seven forward speed ratios derived from three planetary gearsets.
In one aspect of the present invention, each transmission has three planetary gearsets and each planetary gearset has three planetary members.
In another aspect of the present invention, the planetary members are comprised of a sun gear member, a ring gear member, and a planet carrier assembly member.
In still another aspect of the present invention, a first member of the first and second planetary members are interconnected.
In yet another aspect of the present invention, the second member of the second planetary gearset and the first member of the third planetary gearset are continuously interconnected by an interconnecting member.
In a yet still another aspect of the present invention, the second member of the first planetary gearset is continuously interconnected with either a third member of the second planetary gearset or a second member of the third planetary gearset.
In yet still another aspect of the present invention, a member of the first planetary gearset is continuously interconnected with a transmission housing.
In still another aspect of the present invention, a transmission output shaft is continuously interconnected with at least one member of one of the planetary gearsets.
In yet another aspect of the present invention, the input shaft is not continuously interconnected with any member of the planetary gearsets.
In a further aspect of the present invention, six selectively engageable torque-transmitting mechanisms are engaged in combinations of two to establish at least seven forward speed ratios and one reverse speed ratio within the transmission.
In a yet further aspect of the present invention, a first of the torque-transmitting mechanisms interconnects a transmission input shaft with at least one member of one of the planetary gearsets.
In yet a further aspect of the present invention, a second of the torque-transmitting mechanisms selectively interconnects the input shaft with another member of the first or third planetary gearset or with one of the interconnected members.
In still a further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with at least another member of the planetary gearsets or with the input shaft or with the output shaft.
In a yet still further aspect of the present invention, a fourth of the torque-transmitting mechanisms selectively interconnects a member of one of the three planetary gearsets with either the input shaft, the output shaft, or another member of one of the planetary gearsets.
In another aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects a member of one of the three planetary gearsets or one of the fixed interconnections with another member of one of the three planetary gearsets.
In a further aspect of the present invention, a sixth of the torque-transmitting mechanisms connects a member of one of the planetary gearsets with either the output shaft, another member of one of the planetary gearsets, or with the transmission housing.